Baxi 105e pressure problem

[quietman]

Hi guys/gals, my Baxi runs fine if cold set pressure is no more than 0.5bar, pressure increase when hot 1.5bar. If I try to increase the cold pressure to 0.7bar then the hot pressure reaches 3bar and the pressure relief valve drips the excess pressure away. When this happens and the boiler returns to cold the cold pressure is back to 0.5 bar and the boiler runs perfectly well.
So, I guess it's either the expansion vessel pressure needs topping up (boiler is approx 13yrs old) or the vessel has failed and needs changing. Any guesses as to which I'll find tomorrow when I press the shraeder valve?
Thanks for your help/comments.
Ps. Does a replacement vessel come pre-charged?

 

[mrStat]

Hi, yes a replacement vessel comes pre-charged. 50:50 as to whether or not it has totally failed. Just remember step to the side when you press that schraeder valve for when that water squirts out.

 

[Riley]

But you will require a gas safe engineer to fit it to your boiler as you should not be removing the cover legally as this can form a combustion seal that you have no way of testing if it’s refitted properly

 

[mrStat]

If it’s a standard efficiency 105e then the vessel is at the rear and won’t need access to the chamber.

Just remember. Don’t disturb the flue

 

[Riley]

So again a gas safe engineer is probably the way to go

 

[quietman]

Thank you guys for your comments. Fingers crossed that it's a top up required, the 0.5bar pressure when cold gives me a little hope although the replacement procedure doesn't look to much of a problem! I should have mentioned I am a City and Guilds trained Plumber and although I've been out of the trade for about 30yrs I've tried to keep abreast of the changes that have occurred. I believe, and I'm sure you'll correct me if I'm wrong, that the legislation requires a "competent person" in these circumstances so I would hope that I would qualify, after all I do have my own "U" gauge!

 

[Riley]

If you have to remove the flue you have no analyser to test its reassembly. I’m not being awkward if you need a new vessel fit an external one

 

[quietman]

Riley, you're not being awkward at all, I appreciate any advice. I've never fitted an external expansion vessel, if you have any suggestions regarding make I'd be happy to hear them. I believe it would be added like another rad to the system, I could site it next to the boiler. I think the current vessel is either 8ltr or 10ltr. Any input gratefully received. Cheers.

 

[Riley]

Just needs to be of a suitable size cut into the return pipework

 

[Riley]

I’d go to an independent merchant